Commit f549d6c1 authored by Stephen Smalley's avatar Stephen Smalley Committed by Linus Torvalds
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[PATCH] Generic VFS fallback for security xattrs 



This patch modifies the VFS setxattr, getxattr, and listxattr code to fall
back to the security module for security xattrs if the filesystem does not
support xattrs natively.  This allows security modules to export the incore
inode security label information to userspace even if the filesystem does
not provide xattr storage, and eliminates the need to individually patch
various pseudo filesystem types to provide such access.  The patch removes
the existing xattr code from devpts and tmpfs as it is then no longer
needed.

The patch restructures the code flow slightly to reduce duplication between
the normal path and the fallback path, but this should only have one
user-visible side effect - a program may get -EACCES rather than
-EOPNOTSUPP if policy denied access but the filesystem didn't support the
operation anyway.  Note that the post_setxattr hook call is not needed in
the fallback case, as the inode_setsecurity hook call handles the incore
inode security state update directly.  In contrast, we do call fsnotify in
both cases.

Signed-off-by: default avatarStephen Smalley <sds@tycho.nsa.gov>
Acked-by: default avatarJames Morris <jmorris@namei.org>
Signed-off-by: default avatarAndrew Morton <akpm@osdl.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent b5bf6c55

fs/Kconfig

+0 −43
Original line number Diff line number Diff line
@@ -783,28 +783,6 @@ config SYSFS 


	Designers of embedded systems may wish to say N here to conserve space.



config DEVPTS_FS_XATTR

	bool "/dev/pts Extended Attributes"

	depends on UNIX98_PTYS

	help

	  Extended attributes are name:value pairs associated with inodes by

	  the kernel or by users (see the attr(5) manual page, or visit

	  <http://acl.bestbits.at/> for details).



	  If unsure, say N.



config DEVPTS_FS_SECURITY

	bool "/dev/pts Security Labels"

	depends on DEVPTS_FS_XATTR

	help

	  Security labels support alternative access control models

	  implemented by security modules like SELinux.  This option

	  enables an extended attribute handler for file security

	  labels in the /dev/pts filesystem.



	  If you are not using a security module that requires using

	  extended attributes for file security labels, say N.



config TMPFS

	bool "Virtual memory file system support (former shm fs)"

	help
@@ -817,27 +795,6 @@ config TMPFS 


	  See <file:Documentation/filesystems/tmpfs.txt> for details.



config TMPFS_XATTR

	bool "tmpfs Extended Attributes"

	depends on TMPFS

	help

	  Extended attributes are name:value pairs associated with inodes by

	  the kernel or by users (see the attr(5) manual page, or visit

	  <http://acl.bestbits.at/> for details).



	  If unsure, say N.



config TMPFS_SECURITY

	bool "tmpfs Security Labels"

	depends on TMPFS_XATTR

	help

	  Security labels support alternative access control models

	  implemented by security modules like SELinux.  This option

	  enables an extended attribute handler for file security

	  labels in the tmpfs filesystem.

	  If you are not using a security module that requires using

	  extended attributes for file security labels, say N.



config HUGETLBFS

	bool "HugeTLB file system support"

	depends X86 || IA64 || PPC64 || SPARC64 || SUPERH || X86_64 || BROKEN

fs/devpts/Makefile

+0 −1
Original line number Diff line number Diff line
@@ -5,4 +5,3 @@ 
obj-$(CONFIG_UNIX98_PTYS)		+= devpts.o



devpts-$(CONFIG_UNIX98_PTYS)		:= inode.o
 
devpts-$(CONFIG_DEVPTS_FS_SECURITY)	+= xattr_security.o

fs/devpts/inode.c

+0 −21
Original line number Diff line number Diff line
@@ -18,28 +18,9 @@ 
#include <linux/mount.h>

#include <linux/tty.h>

#include <linux/devpts_fs.h>

#include <linux/xattr.h>



#define DEVPTS_SUPER_MAGIC 0x1cd1



extern struct xattr_handler devpts_xattr_security_handler;



static struct xattr_handler *devpts_xattr_handlers[] = {

#ifdef CONFIG_DEVPTS_FS_SECURITY

	&devpts_xattr_security_handler,

#endif

	NULL

};



static struct inode_operations devpts_file_inode_operations = {

#ifdef CONFIG_DEVPTS_FS_XATTR

	.setxattr	= generic_setxattr,

	.getxattr	= generic_getxattr,

	.listxattr	= generic_listxattr,

	.removexattr	= generic_removexattr,

#endif

};



static struct vfsmount *devpts_mnt;

static struct dentry *devpts_root;
@@ -102,7 +83,6 @@ devpts_fill_super(struct super_block *s, void *data, int silent) 
	s->s_blocksize_bits = 10;

	s->s_magic = DEVPTS_SUPER_MAGIC;

	s->s_op = &devpts_sops;

	s->s_xattr = devpts_xattr_handlers;

	s->s_time_gran = 1;



	inode = new_inode(s);
@@ -175,7 +155,6 @@ int devpts_pty_new(struct tty_struct *tty) 
	inode->i_gid = config.setgid ? config.gid : current->fsgid;

	inode->i_mtime = inode->i_atime = inode->i_ctime = CURRENT_TIME;

	init_special_inode(inode, S_IFCHR|config.mode, device);

	inode->i_op = &devpts_file_inode_operations;

	inode->u.generic_ip = tty;



	dentry = get_node(number);

fs/devpts/xattr_security.c

deleted100644 → 0
+0 −47
Original line number Diff line number Diff line 
/*

 * Security xattr support for devpts.

 *

 * Author: Stephen Smalley <sds@epoch.ncsc.mil>

 * Copyright (c) 2004 Red Hat, Inc., James Morris <jmorris@redhat.com>

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License as published by the Free

 * Software Foundation; either version 2 of the License, or (at your option)

 * any later version.

 */

#include <linux/string.h>

#include <linux/fs.h>

#include <linux/security.h>

#include <linux/xattr.h>



static size_t

devpts_xattr_security_list(struct inode *inode, char *list, size_t list_len,

			   const char *name, size_t name_len)

{

	return security_inode_listsecurity(inode, list, list_len);

}



static int

devpts_xattr_security_get(struct inode *inode, const char *name,

			  void *buffer, size_t size)

{

	if (strcmp(name, "") == 0)

		return -EINVAL;

	return security_inode_getsecurity(inode, name, buffer, size);

}



static int

devpts_xattr_security_set(struct inode *inode, const char *name,

			  const void *value, size_t size, int flags)

{

	if (strcmp(name, "") == 0)

		return -EINVAL;

	return security_inode_setsecurity(inode, name, value, size, flags);

}



struct xattr_handler devpts_xattr_security_handler = {

	.prefix	= XATTR_SECURITY_PREFIX,

	.list	= devpts_xattr_security_list,

	.get	= devpts_xattr_security_get,

	.set	= devpts_xattr_security_set,

};

fs/xattr.c

+49 −31
Original line number Diff line number Diff line
@@ -51,20 +51,29 @@ setxattr(struct dentry *d, char __user *name, void __user *value, 
		}

	}



	error = -EOPNOTSUPP;

	if (d->d_inode->i_op && d->d_inode->i_op->setxattr) {

	down(&d->d_inode->i_sem);

	error = security_inode_setxattr(d, kname, kvalue, size, flags);

	if (error)

		goto out;

		error = d->d_inode->i_op->setxattr(d, kname, kvalue, size, flags);

	error = -EOPNOTSUPP;

	if (d->d_inode->i_op && d->d_inode->i_op->setxattr) {

		error = d->d_inode->i_op->setxattr(d, kname, kvalue,

						   size, flags);

		if (!error) {

			fsnotify_xattr(d);

			security_inode_post_setxattr(d, kname, kvalue, size, flags);

			security_inode_post_setxattr(d, kname, kvalue,

						     size, flags);

		}

	} else if (!strncmp(kname, XATTR_SECURITY_PREFIX,

			    sizeof XATTR_SECURITY_PREFIX - 1)) {

		const char *suffix = kname + sizeof XATTR_SECURITY_PREFIX - 1;

		error = security_inode_setsecurity(d->d_inode, suffix, kvalue,

						   size, flags);

		if (!error)

			fsnotify_xattr(d);

	}

out:

	up(&d->d_inode->i_sem);

	}

	if (kvalue)

		kfree(kvalue);

	return error;
@@ -139,12 +148,18 @@ getxattr(struct dentry *d, char __user *name, void __user *value, size_t size) 
			return -ENOMEM;

	}



	error = -EOPNOTSUPP;

	if (d->d_inode->i_op && d->d_inode->i_op->getxattr) {

	error = security_inode_getxattr(d, kname);

	if (error)

		goto out;

	error = -EOPNOTSUPP;

	if (d->d_inode->i_op && d->d_inode->i_op->getxattr)

		error = d->d_inode->i_op->getxattr(d, kname, kvalue, size);

	else if (!strncmp(kname, XATTR_SECURITY_PREFIX,

			  sizeof XATTR_SECURITY_PREFIX - 1)) {

		const char *suffix = kname + sizeof XATTR_SECURITY_PREFIX - 1;

		error = security_inode_getsecurity(d->d_inode, suffix, kvalue,

						   size);

	}

	if (error > 0) {

		if (size && copy_to_user(value, kvalue, error))

			error = -EFAULT;
@@ -153,7 +168,6 @@ getxattr(struct dentry *d, char __user *name, void __user *value, size_t size) 
		   than XATTR_SIZE_MAX bytes. Not possible. */

		error = -E2BIG;

	}

	}

out:

	if (kvalue)

		kfree(kvalue);
@@ -221,12 +235,17 @@ listxattr(struct dentry *d, char __user *list, size_t size) 
			return -ENOMEM;

	}



	error = -EOPNOTSUPP;

	if (d->d_inode->i_op && d->d_inode->i_op->listxattr) {

	error = security_inode_listxattr(d);

	if (error)

		goto out;

	error = -EOPNOTSUPP;

	if (d->d_inode->i_op && d->d_inode->i_op->listxattr) {

		error = d->d_inode->i_op->listxattr(d, klist, size);

	} else {

		error = security_inode_listsecurity(d->d_inode, klist, size);

		if (size && error >= size)

			error = -ERANGE;

	}

	if (error > 0) {

		if (size && copy_to_user(list, klist, error))

			error = -EFAULT;
@@ -235,7 +254,6 @@ listxattr(struct dentry *d, char __user *list, size_t size) 
		   than XATTR_LIST_MAX bytes. Not possible. */

		error = -E2BIG;

	}

	}

out:

	if (klist)

		kfree(klist);

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